Battery conditioner with power dissipater

ABSTRACT

The present application is directed to a power dissipation apparatus including a conductive trace formed on a substrate and to methods of using the power dissipation apparatus. The power dissipation apparatus may be used to dissipate heat generated from electrical current passed through the conductive trace of the power dissipation apparatus. The current may be provided from, for example, a battery conditioner.

RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 121 as a divisionof U.S. application Ser. No. 12/984,951, titled “BATTERY CONDITIONERWITH POWER DISSIPATER,” filed on Jan. 5, 2011, which is hereinincorporated by reference in its entirety.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention is directed to systems and methods of conditioninga battery, and more specifically to systems and methods of discharging abattery and dissipating heat generated from the discharge current.

2. Discussion of Related Art

The performance of batteries of various types, for example,nickel-cadmium (NiCd), nickel metal hydride (NiHM), and lithium ion(Li-ion) may be maintained over a significant period of time by periodicconditioning. The effect of conditioning on the performance of a batteryis dependent on the discharge/usage profile for the battery. In someinstances the performance of a battery may be maintained or improved byperiodically depleting the battery by discharging into a resistive oractive load until a cutoff voltage is reached. After the battery hasbeen depleted, it is then recharged. The energy withdrawn from thebattery during the discharge cycle often generates heat.

SUMMARY OF INVENTION

In accordance with an aspect of the present invention, there is provideda battery conditioner. The battery conditioner comprises circuitryconfigured to withdraw current from a battery and direct the currentinto a power dissipation apparatus comprising a non-conductive substrateand a conductive trace formed at least one of in the substrate and onthe substrate, the conductive trace having a first end coupled to thebattery and a second end, wherein the conductive trace convertssubstantially all of the current from the battery into heat between thefirst end and the second end.

In some embodiments, the non-conductive substrate is formed into theshape of an open ended conduit. The battery conditioner may furthercomprise a fan configured to direct air through the open ended conduitformed from the non-conductive substrate. In some embodiments, theelectrical resistance of the conductive trace between the first end andthe second end conductive trace is variable. In some embodiments thepower dissipation apparatus further comprises at least one switch,electrically connected between a first region of the conductive traceand a second region of the conductive trace and configured to create ashort circuit between the first region of the conductive trace and thesecond region of the conductive trace. In some embodiments the batteryconditioner further comprises a sense resistor, wherein the switchcomprises a transistor configured to short out a section of theconductive trace that interconnects the first region and the secondregion responsive to a signal from the sense resistor indicative of acurrent through the conductive trace being outside of a defined range.In some embodiments the conductive trace has a resistance of betweenabout 1 ohm and about 100 ohms and in some embodiments the conductivetrace has a resistance of between about 2 ohms and about 40 ohms

In some embodiments the conductive trace is dimensioned to self-limit atemperature of the conductive trace to within ±5° Celsius of a definedtemperature when a defined voltage is applied across the first end andthe second end of the conductive trace.

In some embodiments the conductive trace is surrounded by anelectrically insulating material.

In some embodiments the conductive trace has a non-uniformcross-sectional area along a length thereof. In some embodiments theconductive trace comprises a plurality of substantially parallelinterconnected lines of conductive material each having a width andincluding a first subset of substantially parallel interconnected linesof conductive material and a second subset of substantially parallelinterconnected lines of conductive material, the width of each of thesubstantially parallel interconnected lines of conductive material inthe first subset being greater than the width of each of thesubstantially parallel interconnected lines of conductive material inthe second subset.

In some embodiments the power dissipation apparatus is mounted to anexternal surface of the battery conditioner and is in thermalcommunication with the external surface of the battery conditioner.

In some embodiments the conductive trace comprises a plurality ofsubstantially parallel interconnected lines of conductive materialincluding a first subset of substantially parallel interconnected linesof conductive material and a second subset of substantially parallelinterconnected lines of conductive material, a spacing between adjacentsubstantially parallel interconnected lines of conductive material inthe first subset being greater than a spacing between adjacentsubstantially parallel interconnected lines of conductive material inthe second subset. In some embodiments the battery conditioner furthercomprises a fan and an open ended conduit, wherein the non-conductivesubstrate is enclosed in the open ended conduit and the fan isconfigured to direct air through the open ended conduit. In someembodiments the open ended conduit has a non-uniform cross-sectionalarea along a length thereof. In some embodiments, the open ended conduitincludes one or more opening in a wall thereof, the one or more openingsconfigured to provide for air flow into and out of the open endedconduit along a length thereof.

In some embodiments the non-conductive substrate is formed from epoxyimpregnated fiberglass.

In some embodiments the battery conditioner further comprises athermally conductive material enclosed within the substrate.

In some embodiments the conductive trace comprises a first conductivetrace formed on a first side of the substrate, and the power dissipationapparatus further comprises a second conductive trace formed on a secondside of the substrate and electrically connected to the first conductivetrace.

In accordance with another aspect of the present invention, there isprovided a method of conditioning a battery. The method compriseswithdrawing current from the battery, directing the current through apower dissipation apparatus comprising a non-conductive substrate and aconductive trace formed at least one of in the substrate and on thesubstrate, and converting substantially all of the current into heatalong a length of the conductive trace.

In some embodiments the method further comprises adjusting an electricalresistance of the conductive trace. In some embodiments the methodfurther comprises maintaining a current through the conductive tracewithin a defined tolerance band. In some embodiments maintaining thecurrent through the conductive trace within the defined tolerance bandcomprises shorting out a section of the conductive trace responsive to asignal from a sense resistor indicative of a current through theconductive trace being outside of the defined tolerance band.

In some embodiments the method further comprises maintaining atemperature of the power dissipation apparatus within a definedtolerance band. In some embodiments maintaining the temperature of thepower dissipation apparatus within the defined tolerance band comprisesshorting out a section of the conductive trace responsive to atemperature of the power dissipation apparatus being outside of thedefined tolerance band.

In some embodiments the method further comprises dissipating the heat.In some embodiments dissipating the heat comprises conducting heat intoan external surface of a battery conditioner and in some embodimentsdissipating the heat comprises directing air across the conductivetrace.

In accordance with another aspect of the present invention, there isprovided a battery draining device. The battery draining devicecomprises a printed circuit board and a metal trace formed on theprinted circuit board, the metal trace configured to dissipatesubstantially all energy drained from the battery.

In some embodiments the metal trace has a non-uniform cross-sectionalarea along a length thereof. In some embodiments the metal tracecomprises a plurality of substantially parallel interconnected metallines each having a width and including a first subset of substantiallyparallel interconnected metal lines and a second subset of substantiallyparallel interconnected metal lines, the width of each of thesubstantially parallel interconnected metal lines in the first subsetbeing greater than the width of each of the substantially parallelinterconnected metal lines in the second subset.

In some embodiments the battery draining device further comprises atleast one switch, electrically connected between a first region of themetal trace and a second region of the metal trace and configured toelectrically connect and disconnect the first region of the metal traceand the second region of the metal trace. In some embodiments thebattery draining device further comprises a sense resistor, and theswitch comprises a transistor configured to short out a section of themetal trace that interconnects the first region and the second regionresponsive to a signal from the sense resistor indicative of a currentthrough the conductive trace being outside of a defined range.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures is represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1 is a plan view of a power dissipation apparatus according to anaspect of the present invention;

FIG. 2 is a cross-sectional view of an air flow conduit enclosing thepower dissipation apparatus of FIG. 1; FIG. 3 is a plan view of a powerdissipation apparatus according to another aspect of the presentinvention;

FIG. 4 is a cross-sectional view of the power dissipation apparatus ofFIG. 1 along line 4-4 in FIG. 1;

FIG. 5 is a plan view of a power dissipation apparatus according toanother aspect of the present invention;

FIG. 6 is a plan view of a power dissipation apparatus according toanother aspect of the present invention;

FIG. 7 is a block diagram of circuitry included in a battery conditionerin accordance with an aspect of the present invention; and

FIG. 8 is an isometric view of a battery conditioner with a powerdissipation apparatus according to another aspect of the presentinvention mounted to an external surface of a side wall thereof.

DETAILED DESCRIPTION

This invention is not limited in its application to the details ofconstruction and the arrangement of components set forth in thefollowing description or illustrated in the drawings. The invention iscapable of other embodiments and of being practiced or of being carriedout in various ways. Also, the phraseology and terminology used hereinis for the purpose of description and should not be regarded aslimiting. The use of “including,” “comprising,” “having,” “containing,”“involving,” and variations thereof herein is meant to encompass theitems listed thereafter and equivalents thereof as well as additionalitems.

The present disclosure is directed generally to systems and methods forconditioning batteries. The performance and life of a battery or batterypack can be improved and extended by a periodically performedconditioning process including, for example, fully discharging thebattery or battery pack and then recharging it to full capacity.Further, by charging a battery or battery pack to full capacity and thendischarging it while monitoring the amount of power drawn from thebattery or battery pack during discharge, the storage capacity andexpected run time of the battery or battery pack may be known.

In accordance with an aspect of the present disclosure, there isprovided a battery conditioner configured to accept a battery pack,charge the battery pack, and to discharge the battery pack as part of abattery conditioning process. In some embodiments, the batteryconditioner includes a single bay, and in other embodiments, includestwo or more bays, each bay configured to accept one battery pack.Battery packs that may be conditioned in the battery conditioner mayinclude, for example, 32 volt, 2.4 AH NiMH battery packs, although thepresent disclosure is not limited to any particular type of battery packor battery packs having any particular voltage and/or capacity ratings.In some embodiments, a conditioning routine performed by the batteryconditioner may include discharging the 32 volt NiMH battery pack at arate of approximately two Amps. At this discharge rate a total of over60 watts are produced from the discharge of the battery pack. When two32 volt NiMH battery packs are discharged simultaneously, this poweroutput increases to over 120 watts. The power drawn from the dischargingbatteries may be converted into heat. It would be desirable to removethe heat from the battery conditioner to keep the components thereof ata temperature that is consistent with long term reliability.

In accordance with an aspect of the present disclosure, a batteryconditioner is provided with a resistive load comprising a substrateincluding one or more conductive traces. The conductive traces are insome embodiments formed of lines of a film of a metal such as copper,although in other embodiments other types of conductive materials may beutilized. In some embodiments, the substrate comprises a printed wiringboard or printed circuit board comprised of, for example, epoxyimpregnated fiberglass. An advantage of this type of substrate is thatit is relatively inexpensive and may be provided with a conductive traceusing techniques known in the art of printed circuit boardmanufacturing. The one or more conductive traces are formed on a surfaceof the substrate, or in other embodiments, in trenches etched in thesurface of the substrate. In other embodiments, the substrate comprisesa flexible material which is capable of being bent into a shape of anopen ended conduit, for example, a tube. The one or more conductivetraces may be formed on the substrate by screen printing, physical vapordeposition, electrolytic deposition, or any other deposition methodknown in the art.

FIG. 1 illustrates a first embodiment of a power dissipation apparatus100 according to the present invention. The power dissipation apparatus100 includes a substrate 110 onto which is printed a conductive trace120. The conductive trace 120 is printed on the substrate in aserpentine pattern. Although corners of the conductive trace 120 areshown a being sharp 90° corners, it should be appreciated that in otherembodiments, the corners of the conductive trace may be rounded to avoidany localized heating. It should also be appreciated that other (e.g.,rectilinear) configurations may be used, as conductive traces 120 ofdifferent embodiments according to the present disclosure are notlimited to a serpentine configuration. The conductive trace 120 may beprovided with contact pads 130 at the ends thereof to facilitate theelectrical connection of the conductive trace 120 to a source of power,for example, to one or more terminals of a battery or battery pack or topower outputs of a battery conditioner or other electrical device. Forexample, during discharge of a battery or battery pack, the positiveterminal of the battery pack or battery pack would be connected to oneof the contact pads 130, and the negative terminal or ground connectedto the other contact pad 130. In another example, a battery conditionerincludes circuitry such as a current controller between a terminal of abattery and one of the contact pads 130. In some embodiments, in use,substantially all electrical power withdrawn from a battery is convertedto heat in the conductive trace 120.

In one embodiment, a connector may be used to connect a battery orbattery conditioner to the power dissipation apparatus and permit one toeasily remove and/or replace the power dissipation apparatus, ifnecessary. One type of connector that may be used is an FFC typeconnector available from Molex Corporation. It should be appreciatedthat the embodiments of the present disclosure are not limited to anyparticular type of connector, as any connector that is capable of beingused to electrically connect the contact pads 130 to a source of powermay be used instead.

The substrate 110 and conductive trace 120 may be dimensioned to providea desired electrical resistance and desired surface area for aparticular use. In one embodiment, the substrate 110 is substantiallysquare with sides of approximately ten inches in length. In otherembodiments the substrate 110 may be sized and shaped as desired to, forexample, provide a desired surface area, or to fit within a certainenclosure or on a particular surface. In one embodiment, the powerdissipation apparatus 100 includes a conductive trace 120 includingabout 167 interconnected ten inch long lines of one ounce copper (acopper film having a weight of one ounce per square foot—about 1.3 milor 34 microns thick), each line having a width of about 0.05 inches,with about 0.01 inches between each line. This conductive trace 120 hasan electrical resistance of about 20 ohms. It should be noted that aconductive trace 120 with this resistance value is only one possibleembodiment. In some embodiments, the conductive trace 120 has aresistance in the range of from about 1 ohm to about 100 ohms, and inother embodiments, has a resistance in the range of from about 2 ohms toabout 40 ohms Conductive traces in different embodiments of the presentdisclosure are not limited to a particular resistance value or range ofresistance values or to particular dimensions. The conductive trace 120may be dimensioned to provide a desired resistance and surface area fora particular use, for example, to dissipate the power from a battery ofa defined voltage and capacity within a desired time while producingless than a defined increase in temperature of the power dissipationapparatus.

In other embodiments, the power dissipation apparatus 100 can beprovided with a conductive trace 120 on both an upper and a lowersurface. In embodiments where these conductive traces have the samedimensions as that described above, and are electrically connected inparallel, the combination of the conductive traces would have anelectrical resistance of about 10 ohms. In embodiments where the twoconductive traces are electrically connected in series, the combinedelectrical resistance would be about 40 ohms As a first approximation,the temperature rise from room temperature of a surface with a definedamount of power (W) input into it is approximately 100 C°/W/in². For thepower dissipation apparatus 100 described above, the surface area isabout 100 square inches. If the example battery conditioner describedabove was used to discharge a single battery pack and produce 60 W ofpower, and this power was directed through the conductive trace 120 ofthis power dissipation apparatus 100, the temperature rise of the powerdissipation apparatus 100 would be about 60 C.° in still air.

To facilitate the removal of heat from the power dissipation apparatus100, in some embodiments air is forced over the surface of the powerdissipation apparatus 100 by, for example, one or more fans. Providingforced air to cool the surface of the power dissipation apparatus 100described above can provide for sufficient convective heat transfer tolower the temperature rise of the power dissipation apparatus 100 fromabout 60 C.° to about 20 C°. This reduction in the temperature risewould be even more significant for a power dissipation apparatus 100with conductive traces 120 on both an upper and a lower surface due tothe greater surface area of the conductive traces 120 from which themoving air could extract heat. In some embodiments the fan could utilizesome of the power that would otherwise be directed into the powerdissipation apparatus 100, thus reducing the resistive heating of thepower dissipation apparatus 100. It should be appreciated that coolingdevices other than or in addition to a fan, for example, a Peltiercooling module, could be utilized in some embodiments of the powerdissipation apparatus 100.

In some embodiments, as illustrated in the cross-sectional diagram ofFIG. 2, the power dissipation apparatus 100 can be mounted within aconduit 200. The conduit 200 may include walls 210 enclosing the powerdissipation apparatus 100, and a fan 220 to force air through theconduit and out an open end 230 thereof. The walls 210 can be formed ofplastic, metal, or any other suitable material capable of withstandingheat radiated from the power dissipation apparatus 100 while inoperation. In some embodiments, the walls 210 of the conduit 200 can beair impermeable, and in other embodiments, the walls 210 can includeopenings such as holes or slots to provide for air flow into and out ofthe conduit 200 along its length. In different embodiments, the conduitcan have a cross-sectional area perpendicular to the flow of airtherethrough in the form of a circle (in which circumstance the conduitcould be described as a tube), an ellipse, a rectangle, or any othershape. In some embodiments, the conduit may have a substantiallyconstant cross-sectional area along its length, and in otherembodiments, the conduit may have a cross-sectional area that changesalong its length. For example, the conduit 200 of FIG. 2 has across-sectional area that decreases from the side of the conduit inwhich the fan 220 is mounted to the open end 230. In some embodiments,the conduit 200 may be closed on one or both ends.

Where the conduit 200 has a decreasing cross-sectional area, as is shownin FIG. 2, the speed of air flowing through the conduit will increase asit flows from a portion of the conduit with a greater cross-sectionalarea to a portion with a lesser cross-sectional area. This increasedspeed of the air flowing along the length of the conduit facilitates amore even cooling of a power dissipation apparatus 100 mounted in theconduit. As air passes over a first portion of the power dissipationapparatus 100 it absorbs heat, making convective heat transfer from thepower dissipation apparatus 100 to the air less effective for thoseportions of the power dissipation apparatus 100 the heated air nextpasses over. Increasing the speed of the air flow as the air is warmedat least partially compensates for this effect, thereby providing a moreeven cooling of the power dissipation apparatus than would occur if theair flowed over the entire power dissipation apparatus 100 at the samespeed.

In some embodiments, sections of the conductive trace 120 near thecenter of the power dissipation apparatus 100 can heat up to a greaterdegree than sections of the conductive trace 120 near edges of the powerdissipation apparatus 100 upon passage of electrical current through theconductive trace 120. This may be due to sections of the conductivetrace 120 near the center of the power dissipation apparatus 100 beingsurrounded by more other sections of the conductive trace 120 thansections near the edge, or may be due to lesser air cooling of areasnear the center of the power dissipation apparatus 100 than areas nearthe edges. In some embodiments, such as that illustrated in FIG. 3, toeven out the temperature across the surface of the power dissipationapparatus 100, one or more sections 140 of the conductive trace 120 maybe increased in width or thickness relative to other sections.Alternatively, or additionally, the spacing between conductive lines indifferent portions of the conductive trace 120 may be varied tofacilitate the maintenance of a substantially even temperature profileacross the surface of the power dissipation apparatus 100.

In another embodiment, as illustrated in FIG. 4, which is a crosssection of the power dissipation apparatus 100 along line 4-4 of FIG. 1,a thermally conductive layer 105, either buried within the substrate110, present on a side of the substrate opposite that of the conductivetrace 120, or present on a same side of the substrate as the conductivetrace 120, but separated from the conductive trace by an electricallyinsulating layer, can facilitate transporting heat from hotter to coolerareas of the power dissipation apparatus 100. In some embodiments, botha variation in the dimensions or spacing of lines of the conductivetrace and the utilization of a buried thermally conductive layer 105 canbe used to facilitate the maintenance of a substantially eventemperature profile across the surface of the power dissipationapparatus 100.

In some embodiments, the power dissipation apparatus 100 may be providedwith a conductive trace 120 with a variable resistance. In someembodiments, the resistance of the conductive trace 120 may be regulatedto provide a desired current through the conductive trace 120. In thismanner, the power dissipation apparatus 100 can be used in a batteryconditioner to not only dissipate heat produced from discharging abattery, but also to regulate the discharge current from the battery toa desired level.

To provide a conductive trace 120 of a power dissipation apparatus 100with a variable resistance, switches 150, such as field effecttransistors (FETs) can be utilized to short out sections of theconductive trace 120 as desired. In some embodiments, one or more of theswitches 150, may comprise a MOSFET, which may be operated as atwo-state (i.e., on or off) digital switch, or may be operated in alinear (i.e., analog) mode, thereby providing the dissipating apparatuswith a continuously variable effective resistance rather than onlydiscrete values. In other embodiments, one or more of the switches 150may comprise any device capable of providing a range ofcontinuously-variable resistance. An embodiment of such a powerdissipation apparatus 100 is illustrated in FIG. 5. As shown in FIG. 5,multiple switches 150 can be placed between different sections of theconductive trace 120. Closing one or more of the switches 150 wouldshort out a section of the conductive trace, reducing its effectivelength. It should be noted that the embodiment illustrated in FIG. 5 isonly one example. In other embodiments, more or fewer switches 150 maybe present, and these switches may be used to short out longer orshorter portions of the conductive trace 120 than is illustrated in FIG.5.

In other embodiments, one or more switches 150 may be arranged along theconductive trace 120 such that the operation of the one or more switches150 may alter an electrical connection between one or more portions ofthe conductive trace from a serial configuration to a parallelconfiguration. For example, a second set of switches 150′ shown inphantom in FIG. 5 may additionally be provided to permit sections of theconductive trace to be switched into various parallel and seriescombinations. This may enable all portions of the conductive trace to beutilized, even when a resistance for the conductive trace is desiredthat would be less than that exhibited by the conductive trace with allportions electrically connected in series.

Running the heat dissipation apparatus with portions of the conductivetrace electrically connected together in various serial and parallelconfigurations may allow for heat to be dissipated over a greater areaof the conductive trace than could be attained when operating the heatdissipation apparatus with one or more sections of the conductive traceshorted out.

In one embodiment, the switches can be controlled by a microprocessor160. In one embodiment, the microprocessor 160 can include a 12 bitinternal analog to digital converter and a 4 bit output port. Thismicroprocessor would be capable of controlling 16 switches 150 (or 16combinations of switches 150) using a 4-16 line decoder. Themicroprocessor can read a voltage across a sense resistor 170, forexample, a 25 milliohm resistor, to calculate the current through theconductive trace 120, and open or close various ones of switches 150until a desired current through the conductive trace 120 is achieved. Insome embodiments, current through the conductive trace may be measuredby one or more alternative or additional techniques. For example, a Halleffect sensor could be used in addition to or as an alternative to thesense resistor 170 to measure a current through the conductive trace120.

The microprocessor 160, sense resistor 170, and switches 150 cancommunicate via electrical conductors located on an opposite side of thesubstrate 110 from the conductive trace 120, or insulated from theconductive trace by an electrically insulating material, such as apolymer film. In some embodiments wherein the substrate comprises amulti-layer material, the microprocessor 160, sense resistor 170, andswitches 150 can communicate via electrical conductors located betweenlayers of the substrate. Additional heat dissipating conductive tracesmay also be present between layers of a multi-layer substrate. Inaccordance with some aspects of this embodiment, the power dissipationapparatus 100 of FIG. 5 is capable of maintaining a discharge currentthrough the conductive trace 120 within about plus or minus threepercent.

In other embodiments, the sense resistor 170 may comprise a thermistor,and the microprocessor 160 may control the switches 150 in response to asignal from the thermistor 170 to adjust the length (and resistance) ofthe conductive trace 120 to maintain a temperature of the powerdissipation apparatus 100 within a desired range. It should also benoted that many conductive materials exhibit an increase in resistivityas they are heated. For example, the electrical resistivity of copperincreases by about 0.4% per degree Celsius. As such, in someembodiments, the conductive trace 120 may be formed of a material whoseelectrical resistance increases with temperature, and thus would becomemore resistive as more current is passed through it. The conductivetrace 120 could thus self regulate the amount of current that passesthrough it. In some embodiments, the conductive trace 120 would selfregulate the current passing through it to within plus or minus threepercent and/or self regulate its temperature to within plus or minusfive degrees Celsius of a desired level without external control.

In another embodiment, illustrated in FIG. 6, the substrate 110 may beformed of a flexible material. A conductive trace 120 can be formed onone or both sides of the substrate, or in some embodiments, between twolayers of flexible substrate material. In some embodiments, the flexiblesubstrate material comprises an electrically insulating polymericmaterial. The first and second layers of flexible substrate material maybe formed from the same polymeric material, or from different materials.One or both of the inner surfaces of the electrically insulatingpolymeric material may be coated with an adhesive, and the entireassembly vulcanized in a heated press, such as a heated vacuum press, toform an integrated assembly. It should be appreciated that other methodsof manufacture may alternatively be used, as embodiments of the presentdisclosure are not limited to any particular process.

The substrate may be rolled into a tube or a conduit of another shape,and a fan 220 may be placed at one end of the conduit to direct airthrough the conduit and cool the conductive trace 120 when current isbeing passed therethrough. Forming a conduit from the rolled substrateto direct air along a surface of the conductive trace 120 (or along afilm covering a surface of the conductive trace) eliminates the need fora separate structure to direct air over the substrate such as theconduit 200 of FIG. 2. Like the conduit of FIG. 2, the conduit formed ofthe flexible substrate may have a non-uniform cross section along itslength, and like the power dissipation apparatus of FIG. 5, the flexiblesubstrate may accommodate a microprocessor 160, switches 150, and asense resistor 170 to provide for selectively shorting out portions ofthe conductive trace 120. In different embodiments, one or more elementsof the circuitry including the microprocessor 160, switches 150, andsense resistor 170 may be disposed on the substrate 110 or on a separatecircuit board.

In one embodiment, the flexible substrate may be formed from a foilresistance material surrounded by an electrically insulating material,such as Kapton® polyimide film, available from E.I. du Pont de Nemoursand Company. Kapton®, a registered trademark of E.I. du Pont de Nemoursand Company, is a polyimide film possessing excellent physical andelectrical properties. It has superb chemical resistance; there are noknown organic solvents for the film, it is certified to meet therequirements of MIL-P-46112 B and of ASTM D-5213-99, and it does notmelt or burn. It has the highest UL-94 flammability rating: V-O. Kapton®polyimide film is rated for continuous operation from −269° C. (−452°F.) to 400° C. (752° F.), has a dielectric strength of approximately7000 volts/mil at 25° C., has no significant thermal expansion orcontraction properties, and has no known particle generating properties.Although Kapton® and Kapton® MT, and Kapton® MTB are used in someembodiments as the electrically insulating material, other types ofinsulating materials, such as any other suitable polymer, rubber,plastic, or thermoplastic material may be used. Preferably, theseelectrically insulating materials are strong, have a high chemicalresistance, do not melt or burn, possess minimal thermal expansion andcontraction properties, and remain flexible over a wide temperaturerange. Further, it is preferred that the electrically insulatingmaterial have a relatively low thermal impedance, such that some of theheat generated by the conductive trace 120 is transferred through theelectrically insulating material. It should be appreciated that not allof these properties may be required, such that other polymeric orinsulating materials may be used. For example, in applications whereexposure to reactive chemicals is unlikely, materials possessing lowerchemical resistance may be used.

The power dissipation apparatus 100 may be utilized in conjunction witha battery conditioner, which in some embodiments includes circuitelements such as those schematically illustrated in FIG. 7. The batteryconditioner 300 may include a controller 310, comprising amicroprocessor, ASIC, PLC controller, or any other electronic controllerknown in the art. The controller 310 is in electrical communication withboth a battery charge circuit 320 and a battery discharge circuit 330.The charge and discharge circuits 320 and 330 are in electricalcommunication with a battery interface 340. The battery interfaceincludes connections for delivering power to the battery from the chargecircuit 320 and for delivering power from the battery to the dischargecircuit 330. The battery interface 340 may also include a communicationsbus, such as an SM bus, for providing communications from a battery,such as a smart battery, connected to the battery interface 340 to thecharge and/or discharge circuits 320, 330, or in some aspects directlyto the controller 310. These communications may include, for example, anidentification of the battery type or charge/discharge history of thebattery, which may be utilized by the battery conditioner to determinean appropriate charge or discharge profile for the battery.

The controller 310 may also be in communication with a temperaturesensor 350. Temperature sensor 350 is placed proximate a battery, and insome embodiments in contact with a battery, while the battery is presentin a battery well in the battery conditioner to provide the controller310 with an indication of the temperature of the battery. Monitoring thetemperature of the battery may provide for the controller 310 to abort acharge or discharge process if the battery becomes dangerously hot. Insome embodiments, a smart battery connected to the charger may includeits own temperature sensor, in which case the battery may communicateits temperature directly to one of the charge circuit 320, dischargecircuit 330, or controller 310, rendering the temperature sensor 350superfluous. In some embodiments, the temperature sensor 350 can beutilized to perform a check or a calibration on a temperature sensorincluded in a smart battery coupled to the battery conditioner.

The discharge circuit 330 may be connected to a resistive load, such asthe power dissipation apparatus 100. Current drawn from the batteryduring discharge would be passed via the discharge circuit through thepower dissipation apparatus 100. In some embodiments, the controller 310can also be in electrical communication with the power dissipationapparatus, for example with a temperature sensor in the powerdissipation apparatus, with the controller 160 of the power dissipationapparatus, with the sense resistor 170, or with one or more switches150. This allows the controller 310 to control the operation of the oneor more switches 150 to adjust the resistance of the power dissipationapparatus circuit path, to monitor the current or voltage applied to thepower dissipation apparatus, or to monitor the temperature of the powerdissipation apparatus and instruct the discharge circuit 330 to alterthe power applied to the power dissipation apparatus as needed, such aswhere the power dissipation apparatus is exceeding a desiredtemperature.

In different aspects, one or more of the circuit elements 310, 320, and330 can be formed on the same circuit board, or on different circuitboards, or as parts of the same or different integrated circuits. Insome aspects the power dissipation apparatus 100 can reside within thebody of a battery conditioner 300 or other device, for example, mountedto an internal surface of a wall of the battery conditioner 300 or otherdevice. A fan (not shown) may also be present within the body of thepower dissipation apparatus to direct air across the power dissipationapparatus to remove heat therefrom. Vents can be provided in the body ofthe battery conditioner to permit cool air to enter and to allow warmair to exit the interior of the body of the battery conditioner. In someaspects the power dissipation apparatus 100 may be formed on a samecircuit board as any one or more of the circuit elements 310, 320, 330,340, or 350.

In a further embodiment, the power dissipation apparatus 100 may bemounted to an external surface of a piece of equipment, such as to anexternal side of a wall of a battery conditioner. This is illustrated inFIG. 8, where a power dissipation apparatus 100 is mounted to anexternal side of a side wall of a battery conditioner 300. Alsoillustrated in FIG. 8 is a battery bay 360 formed in the upper surfaceof the battery conditioner into which batteries to be conditioned can beplaced, as well as a display/control panel 370 which may be used as auser interface for the battery conditioner 300.

Various structures may be used to mount the power dissipation apparatus100 to the wall of the battery conditioner. For example, thermallyconductive adhesives or adhesive tapes, such as Thermally ConductiveAdhesive Transfer Tapes 8805, 8810, 8815, 8820, available from 3MCorporation, may be used to mount the power dissipation apparatus 100 toa wall of the battery conditioner.

Mounting the power dissipation apparatus 100 to the side wall of abattery conditioner 300 provides for the external surface of the batteryconditioner 30 to serve as a heat sink from which heat may be withdrawnfrom the power dissipation apparatus by thermal conduction. Inadditional embodiments, the power dissipation apparatus 100 mounted tothe side wall of a battery conditioner 300 may be at least partiallyenclosed by walls 210 forming a conduit, such as conduit 200 of FIG. 2.This conduit may have one or more fan units 220 to provide a flow of airthrough the conduit and out an open end 230 thereof.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe invention. Accordingly, the foregoing description and drawings areby way of example only.

What is claimed is:
 1. A battery draining device comprising: a printedcircuit board; and a metal trace formed on the printed circuit board,the metal trace configured to dissipate substantially all energy drainedfrom the battery.
 2. The battery draining device of claim 1, wherein themetal trace has a non-uniform cross-sectional area along a lengththereof.
 3. The battery draining device of claim 2, wherein the metaltrace comprises a plurality of substantially parallel interconnectedmetal lines each having a width and including a first subset ofsubstantially parallel interconnected metal lines and a second subset ofsubstantially parallel interconnected metal lines, the width of each ofthe substantially parallel interconnected metal lines in the firstsubset being greater than the width of each of the substantiallyparallel interconnected metal lines in the second subset.
 4. The batterydraining device of claim 1, wherein the battery draining device furthercomprises at least one switch electrically connected between a firstregion of the metal trace and a second region of the metal trace andconfigured to electrically connect and disconnect the first region ofthe metal trace and the second region of the metal trace.
 5. The batterydraining device of claim 4, further comprising a sense resistor, whereinthe switch comprises a transistor configured to short out a section ofthe metal trace that interconnects the first region and the secondregion responsive to a signal from the sense resistor indicative of acurrent through the metal trace being outside of a defined range.
 6. Thebattery draining device of claim 1, further comprising circuitryconfigured to connect to the battery and direct current from the batterythrough the metal trace.
 7. The battery draining device of claim 1,wherein the printed circuit board is formed into the shape of an openended conduit.
 8. The battery draining device of claim 7, furthercomprising a fan configured to direct air through the open ended conduitformed from the printed circuit board.
 9. The battery draining device ofclaim 1, wherein an electrical resistance of the metal trace between afirst end of the metal trace and a second end of the metal trace isvariable.
 10. The battery draining device of claim 9, wherein the metaltrace has a resistance of between about 1 ohm and about 100 ohms. 11.The battery draining device of claim 10, wherein the metal trace has aresistance of between about 2 ohms and about 40 ohms.
 12. The batterydraining device of claim 9, wherein the metal trace is dimensioned toself-limit a temperature of the metal trace to within ±5° Celsius of adefined temperature when a defined voltage is applied across the firstend and the second end of the metal trace.
 13. The battery drainingdevice of claim 1, wherein the metal trace is surrounded by anelectrically insulating material.
 14. The battery draining device ofclaim 1, mounted to an external surface of a battery conditioner and inthermal communication with the external surface of the batteryconditioner.
 15. The battery draining device of claim 1, wherein themetal trace comprises a plurality of substantially parallelinterconnected lines of conductive material including a first subset ofsubstantially parallel interconnected lines of conductive material and asecond subset of substantially parallel interconnected lines ofconductive material, a spacing between adjacent substantially parallelinterconnected lines of conductive material in the first subset beinggreater than a spacing between adjacent substantially parallelinterconnected lines of conductive material in the second subset. 16.The battery draining device of claim 1, further comprising a fan and anopen ended conduit, wherein the printed circuit board is enclosed in theopen ended conduit and the fan is configured to direct air through theopen ended conduit.
 17. The battery draining device of claim 16, whereinthe open ended conduit has a non-uniform cross-sectional area along alength thereof.
 18. The battery draining device of claim 16, wherein theopen ended conduit includes one or more openings in a wall thereof, theone or more openings configured to provide for air flow into and out ofthe open ended conduit along a length thereof.
 19. The battery drainingdevice of claim 1, further comprising a thermally conductive materialenclosed within the printed circuit board.
 20. The battery drainingdevice of claim 1, wherein the metal trace comprises a first conductivetrace formed on a first side of the printed circuit board, the batterydraining device further comprising a second metal trace formed on asecond side of the printed circuit board and electrically connected tothe first metal trace.